I have a Stock 1990 si EF with a d16a6 (stock intake, stock exhaust to cat etc, etc etc...) and for the last week when its been really hot out after driving for a bit usually highway i will get off the highway and i can feel it randomly missing at idle and acceleration (all speeds and throttle input) besides it being annoying and lightly jolting the car with a very slight smell of unburnt fuel. there are no other issues. it idles perfect doesnt overheat doesnt hesitate, tach needle sits solid and doesnt go erratic. I pulled the plugs and they look awesome no signs of a rich or lean condition. the car has had the following done maintenance wise.


new timing belt and waterpump
new radiator and tstat and hoses
new plugs, cap and rotor
new ignition coil
new valve cover gasket and tube seals
valve adjustment 2k ago before the issue popped up
new temp sensor for the ecu
new fan switch sensor


anyone ever ran into this issue or have any advice on components to check? I know it has to do with the hot weather outside because in the morning when its less than 100* OAT there is no miss and the car runs amazing even after a 30+ mile drive.

 

Which temp sensor for ECU are you referring to?
How is your air filter doing?
Have you check the ignition timing lately?

 

air filter is brand new and clean, the coolant temp sensor. and ignition timing was set after the tbelt so about a month but ill recheck that at work.

 

May want to check out the IAT too.
It's the white sensor on the side of the intake manifold.
A bad IAT will increase start-up time as well as increase fuel consumption after warm up.
When it goes completely bad, the ECU will throw a code and you will have a check engine light.

 

will check that out. any other ideas? no extended start times or bad mpgs at all. not getting any CEL or codes from the led on the ecu

 

O2 sensor could be getting lazy.
Injector spray pattern could be fouled.